The object of the invention is to provide an apparatus which is capable of providing an accurate, fine-tuneable adjustment of a valve while at the same time being not easily influenced by possible impurities in the form of particles in the fluid flowing through the apparatus. A further object is to provide an apparatus, which in one embodiment could be utilized as a flow meter or quantity gauge.
In the petroleum production industry, for example, there is an ever-increasing need for the ability to dose a fluid, such as a liquid chemical, into another medium, a so-called chemical injection. Further, there is an expressed wish and need for the ability to automate and remotely control the chemical injection systems.
Today there are systems commercially available, and also systems known from the patent literature, describing the dosing of fluids into, for example, hydrocarbon wells by the use of different control valves. Such control valve may for example be a damper, a choke, a needle and a gate control valve, also by the use of thermally sensitive and self-adjusting control valves. Examples of such systems are disclosed in publications CA 2 483 399, U.S. Pat. Nos. 6,745,838, 4,565,215, WO 97/34116, WO 2004/016904 and WO 94/25188, EP 1 355 169 and GB 2 276 675. However, it turns out that all the control valves shown in the above-mentioned publications, and systems which are commercially available, have at least one of the drawbacks mentioned in what follows.
In the automation and remote control of, for example, chemical injection there is a need for an actuator, which is arranged to regulate the amount of fluid, which is injected into a fluid flow. It is normal that such actuators are constituted by one or more electric, hydraulic or pneumatic motors which is/are connected to a control valve. This represents drawbacks related both to the space requirement and to repair and maintenance, which will necessarily have to be carried out on mechanically movable parts over time. To have control over the amount of fluid injected, there is additionally the need for a flow gauge or a so-called “flow meter” which needs to be connected to a portion of the conduit in which the injection fluid is conveyed. Such a flow meter is relatively space demanding, introduces many complex and maintenance-demanding parts and represents a considerable drawback both in the investment phase and in the operation phase.
A substantial proportion of the dosing systems used in the injection of chemicals are sensitive to the viscosity of the chemicals, which is, in turn, influenced by temperature, so that the viscosity increases when the temperature falls. To avoid too high a viscosity, there may therefore be the need to provide the supply system of the chemicals with heat and/or insulation, which represents in turn economic and operational drawbacks.
A number of the known regulating systems have turned out to be sensitive to impurities because of narrow flow areas, for example in the so-called “orifice”. Therefore, to avoid impurities, there is a need for a filter system retaining impurities. Such filter systems require servicing in the form of relatively frequent replacement of filters. This represents a particularly great disadvantage where the access to the filter system is difficult or limited.
Publication CN 201818582 U discloses an automatic feeding mechanism for a cutting device wherein the feeding mechanism is controlled by means of a hydraulic valve.
The present inventor has invented an apparatus that has proven to at least reduce one or more drawbacks of prior art apparatuses. The apparatus is disclosed for example in publication WO 2007148978 A1 describing inter alia a regulating device for regulating a fluid flow, the regulating device comprising an actuator element including a first restriction device, and a regulating device body including a second restriction device and forming, together with said first restriction device, the choke device of the regulating device, the regulating device being provided with a flow area arranged to convey fluid between a fluid inlet and a fluid outlet, and the actuator element or regulating device body being disposed at least in a portion of the regulating device body and actuator element, respectively, wherein the actuator element and regulating device body are connected in such a way that the actuator element and the regulating device body are arranged to move freely independently of each other in consequence of a material expansion or material contraction, the through-put of the choke device being indirectly influenced by an energy source which is arranged to supply energy to at least one of the actuator element and/or regulating device body.
The publications U.S. Pat. Nos. 3,650,505 A, 4,487,213 A and 3,211,414 A disclose apparatuses that have some common features with the apparatus disclosed in the publication WO 2007148978 A1.
The apparatus disclosed in WO 2007148978 A1 has proven to be satisfactory in view of other known prior art apparatuses disclosed in the publications mentioned above. However, the inventor has identified that improvements of said apparatus are possible in order to further remedy or at least reduce one or more drawbacks of the prior art apparatuses.
A further improvement in view of the apparatus disclosed in WO 2007148978 A1, is related to providing an easily replaceable valve that may, if desirable, be of an off-the-shelf type. The apparatus in WO 2007148978 A1 discloses a “tailor-made” valve being fully integrated within the apparatus.
Another improvement to the apparatus disclosed in WO 2007148978 A1 is that the apparatus in accordance with the present invention may be more responsive. The apparatus in WO 2007148978 A1 is based on a “tube-in-tube” arrangement, meaning that the dimension of the outer tube is highly dependent on the dimension of the inner tube and the annular space between the inner tube and the outer tube. A person skilled in the art will appreciate that a wall thickness of a tube being subject to a pressure also depends on the diameter of the tube. In the apparatus disclosed in WO 2007148978 A1, the wall thickness of the outer tube is therefore relatively large, with a less responsive apparatus as a result. Further, such a tube-in-tube arrangement results in the temperature of the fluid flowing into the apparatus influences to some extent the temperature of the fluid flowing out of the apparatus.
The apparatus disclosed in WO 2007148978 A1 is operated in a 1:1 manner, meaning that the opening and closing of the restriction device (valve) depends on material expansion or contraction of an actuator element in a 1:1 relationship. Such a 1:1 relationship may result in an apparatus being less fine-tunable and/or less responsive.